A phosphoenolpyruvate-dependent sucrose phosphotransferase system has been identified in Streptococcus mutans. Sucrose phosphotransferase activity was inducible by sucrose and had an apparent Km for sucrose of 70 microM. The product of the sucrose phosphotransferase reaction was isolated and identified as sucrose phosphate. Additional analysis revealed that the phosphate group was on the glucose moiety. Mutants unable to grow in media containing low concentrations of sucrose were isolated and found to be missing either sucrose phosphotransferase activity or the ability to hydrolyze sucrose phosphate.